SLIDE 1
August 2017
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Overview of A.W. Faber-Castell Slide Rule Dating Chronology 1892-1920
Colin Tombeur
Background This article is one of a series which details the early slide rules of A.W. Faber-Castell (hereafter referred to as Faber). The series, by Trevor Catlow and myself, is based on our research collaboration and the resulting development and analysis of a database of slide rule specimens, as described in [1]. Although Faber began production with just one known slide rule model, they quickly developed their designs, production processes and model range. Due the scarcity of detailed reliable information, dating these slide rules before Faber introduced blind date stamps has been difficult. Trevor’s 2009 JOS article [2] and subsequent 2013 update [3] were the first major steps in rectifying this situation. Although broadly correct, Trevor’s findings were based largely on the limited number of slide rules from this time in his collection. As a result his scope was limited, a fact that he acknowledged in his articles. Our collaboration has produced a more comprehensive chronology of changes to features on these early slide rules, based on the study of many more specimens, cataloguing and dating as many changes as possible. This article gives an overview of feature changes between the beginning of slide rule production in 1892 [4] and the introduction of date stamps on the rules in 1920 [5]. We have been able to supply an approximate year, or span of years, for the changes, which we believe to be accurate to within a year or so. Planned further articles in the series will describe particular areas of focus and the chronology of feature changes in much greater detail. A slide rule can only be as old as the introduction of its most recent feature, and as young as the earliest time a feature present on it was phased out. [1] A slide rule without a blind stamp can be given an approximate date range of the completion of its manufacture by comparing and aligning its features with the Chronology Chart below. In theory all of the date ranges of features on a specimen should overlap at some point on the chart and an approximate date of manufacture can easily be established. Occasionally however, due to peculiarities in the design and manufacturing process this is not the case, but a manufacture date can still be estimated using the above guideline from the latest overlapping range of features. Particular care should be taken when considering cursors and boxes which may have been replaced with non-original items. Unless a definite connection can be established, for example by the addition of names or dates by a previous owner, these items should be considered as confirming, rather than defining, the dating. Introducing the Chronology Chart The Chronology Chart has rows detailing slide rule features, grouped into the following five categories: STOCK & SLIDE, SCALES, CURSOR, TEXT & LABELS and BOX. Each feature may have several manifestations. Some of the features have references to chart notes, either a single character for further description, e.g. (a), or two characters for picture examples, e.g. (aa). The columns indicate an approximate year, or year range, when a change occurred, ‘Change Point’, prefixed with ‘c’ (circa). Where it has not been possible to define change points unambiguously for certain features, some year ranges overlap others. Such cases are highlighted in light blue, and special care should be taken when comparing features around these points. In the main body of the chart, features that are present at the change points are indicated by solid green
- shading. Thus an approximate start point, when the feature first appeared on slide rules, and end point